Percussion drilling apparatus



Oct. 27, 1964 L. B. WILDER ETAL PERCUSSION DRILLING APPARATUS Filed July19, 1961 2 Sheets-Sheet 1 FIG. 3

INVENTORS REN/C F. VINCENT LAWRENCE B. WILDER A TTORNEY-' Oct. 27, 1964B. WILDER ETAL PERCUSSION DRILLING APPARATUS 2 Sheets- Sheet 2 FiledJuly 19, 1961 a .2 RCM 0, TNR NEW V W ATTORNE Y United States Patent3,154,153 I ERCUSSEGN DRILLING APPARATUS Lawrence E. Wilder and Renic IVincent, Tuisa, @lda, assignors to Pan American Petroleum Corporation,Tulsa, @ida, a corporation of Delaware Fitted July 19, 1961, Ser. No.125,218 Qlaims. (Cl. 173-43) This invention concerns a fluid-actuateddevice used to apply percussive blows to a rotary drill bit whiledrilling hard materials such as geologic formations. More particularly,the invention relates to valve designs for percussion motors whichenable the pressure of the motive fluid to be applied to the motorhammer for a greater portion of the distance travelled by the hammer.

A substantial increase in drilling rate can be obtained if percussiveblows are applied to a rotary drill bit. This technique has been used togreat advantage in drilling shot holes for seismic exploration andquarrying operations as well as in drilling oil and gas wells. Thepercussive energy is usually obtained from a motor in the drill stringimmediately above the bit. Power fluid pumped down the drill pipe drivesthe motor and is exhausted through the bit to remove drilled materialfrom the vicinity of the bit. Basically, these percussion motors containa hammer element which is reciprocated by the power fluid, striking ananvil which transmits the energy to the bit. It has been found that aminimum or threshold quantity of energy must be delivered to the bit tostress the rock beyond its elastic limit and produce chips, i.e., drill.Limitations on the size of the apparatus which can be run in a well havemade it dificult to design a tool Which will operate efficiently anddeliver adequate energy to the bit. Complex valve systems have beendevised to increase the power delivered to the bit by the percussionmotor. In general, these have been unsatisfactory because they aredifiicult to manufacture and, owing to space limitations, they cannot bedesigned to withstand rugged use for long periods of time. Mechanicalelements of the intricate apparatus frequently fail after brief periodsof operation.

Many of the prior art tools have used a differential area hammer. Inthese tools high-pressure gas is applied to opposed, unequal areas ofthe hammer, causing it to move in the direction responsive to thepressure on the larger area. The net force applied to the hammer isproportional to the differential area. It is therefore advantageous tomake the differential area as great as possible, considering thelimitations on overall size of the tool. This is illustrated in thefollowing relationship for determining the kinetic energy of the hammerdur ing its downstroke.

where:

P-=Differential pressure across the hammer A=Net area of hammersubjected to the differential pressure W=Weight of hammer S=Distancetravelled by hammer with the differential pressure across the hammerThis relationship shows that kinetic energy per blow of the hammer canbe increased either by applying the force (PA+W) over a greater distanceS or by increasing the force component (PA-l-W). Also, the total energydelivered by the hammer can be increased by increasing A whilemaintaining the other variables constant, thereby increasing thefrequency of the hammer blows without decreasing the energy per blow.Owing to the limitations on space, and the desire to recover the maximumpotential energy from the power fluid, the above relationr hi ni fiPatented Get. 27, l fid "ice ship suggests application of thedifferential pressure across the entire area of the hammer through asgreat a distance as possible.

It is an object of our invention to produce a gasoperated percussiontool with a hammer element having top and bottom end surfaces of equalarea. It is a further object to provide means for exhausting gas fromalternate ends of the percussion hammer while simultaneously applyinggas pressure to the opposite end. Another object is to provide a valvesystem which maintains the pressure differential across the hammer for agreater portion of the distance travelled by the hammer.

These and other objects are accomplished by the apparatus describedherein.

In general, our invention consists of a gas-operated percussion drillingtool having an equal-area hammer which reciprocates within a housing asgas circulates through the hammer and discharges through a bit below thepercussion tool. By equal-area, we mean a hammer having top and bottomsurfaces of the same area. Also, we provide a quick-acting, slidingvalve at the gas inlet which increases substantially the distancetravelled by the hammer under the influence of differential pressure anddecreases the distance it must travel by momentum at the expense ofkinetic energy. Additionally, we have devised a moving finger valvewhich delays the opening and closing of the exhaust ports at the ends ofthe hammer, thereby further increasing the distance through which thedifferential pressure is applied to the hammer.

FIGURE 1 is a cross-sectional view of the percussion tool at a time whenthe hammer is being raised.

FIGURE 2 shows the elements of the percussion tool during the downstrokeof the hammer.

FIGURE 3 shows the annular passageways in the tool along line 3--3 ofFIGURE 1.

FIGURE 4 is a similar view showing the passageways in the tool alongline 4-4 of FIGURE 2.

FIGURE 5 is a cross-sectional view, taken along line 55 in FIGURE 2,showing the arrangement of the elements at the lower end of the tool.

The percussion tool has a housing 10 with tool joint connections 11 atthe top and bottom in order that the tool may be installed in a drillstring between the pipe and a bit. Hammer 14 is arranged forreciprocation in the housing to deliver percussive blows to anvil 15which is rigidly connected to drill bit 12. Splined connection 17between anvil 15 and adapter 16 transmits rotary motion from the drillpipe and housing to the bit while permitting limited longitudinalmovement of the anvil-bit assembly in response to impact blows by thehammer. Finger valve 27 is arranged for longitudinal movement along theaxis of the hammer. Flange 26 on the finger valve limits its movementwithin the confines of cylinder 24-. Fluid pressure above the hammer istransmitted to the lower side of flange 26 by way of upper port 22,annular passageway 23 and ports 44 through the wall of cylinder 24 inthe upper end of the hammer. Fluid pressure below the hammer istransmitted similarly to the upper side of flange 26 by way of lowerport 25 and slots 42. In this structure, the finger valve is positionedwithin the hammer in response to the differential pressure across thehammer. Exhaust passageway 32 in the anvil receives the lower end offinger valve 27 in a fluidsealing engagement. Finger valve seat 35 inupper head 36 receives the upper end of the finger valve to stop theexhaustion of fluid from the chamber above the hammer.

Slide valve 29 surrounds the hammer. Ports 30 in the valve admit powerfluid from inlet passageway 31 to annular recess 28 in the hammer. Theslide valve is arranged for longitudinal movement in response to thedifferential pressure between upper fluid conduit 34 and lower fluidconduit 33.

Upper and lower guide members, 37 and 33, respectively, keep the hammerin axial alignment to prevent wobbling and damage as well as providing ahammer seal. Guide members 39, 4t) and 41 hold the slide valve in properalignment.

The operation of the percussion motor will be described with referenceto the figures. A fluid under pressure is circulated down the drill pipeand enters the upper end of housing 10. The fluid flows through inletpassageway 31 to ports 30 in the slide valve then to annular recess 28in the hammer. In the position shown in FIGURE 1, the fluid above thehammer is vented through finger valve 27, exhaust passageway 32 and bitcourses 13, whereas the lower end of the finger valve prevents the flowof fluid from below the hammer into exhaust passageway 32. Thus, thedifferential pressure across the hammer and slide valve 29 holds thelatter in its upper position and lifts the hammer toward upper head 36.Additionally, the differential pressure acting on flange 26 in cylinder24 holds the finger valve in its lower position whereby the lower end ofthe valve will prevent the escape of pressure fluid from below thehammer until the hammer is near upper head 36. As the hammer approachesthe top of its stroke, the upper end of annular recess 28 in the hammerclears the top edge of slide valve 29, permitting highpressure fluid toenter upper fluid conduit 34. Very soon thereafter the lower end of thefinger valve is withdrawn from exhaust passageway 32 and the lower endof annular recess 28 enters the slide valve. It will be seen that thehigh-pressure fluid below the hammer rapidly exhausts to a low-pressurelevel. Simultaneously, the pressure above the hammer starts to increase,causing the slide valve to move quickly to its lower position and thefinger valve to rise to its upper position with the upper end extendinginto valve seat 35. The rapid reversal of the differential pressureacross the hammer decelerates the hammer and ultimately reverses itsdirection of travel.

As the hammer starts its downward movement, the components are in thepositions shown in FIGURE 2. The hammer is driven downward until itcontacts the upper face of the anvil and delivers its kinetic energy.Immediately preceding the cont-act of the hammer with the anvil, thelower edge of the annular recess clears the lower end of the slide valveand the upper edge of the recess enters the slide valve. Also, the upperend of the finger valve is withdrawn from valve seat 35 immediatelypreceding the impact of the hammer with the anvil. This sequence ofevents produces a quick reversal in the differential pressure, causingthe slide valve to rise and the finger valve to drop, thereby startinganother cycle in the operation of the percussion tool.

Referring now to FIGURE 3 for a description of the fluid conduits at theupper end of the hammer, it can be seen that fluid pressure in cylinder24 above flange 26 is equalized with that below the hammer by way ofslots 42 in the upper end of the hammer, annular passageway 43 betweenthe cylinder wall and upper head 21 of the hammer, and lower ports 25.Fluid pressure above the hammer equalizes with that below the flangethrough upper ports 22, annular passageway 23 and ports 44 in thecylinder wall. Ribs 45 centralize and stabilize upper guide member 37 inhousing It). Ribs 46 provide a pressure seal between inlet passageway 31and upper fluid conduit 34.

FIGURE 4 illustrates particularly the structure of the slide valve. Inthis embodiment there are several ports 30 spaced radially about thevalve member. Power fluid flows from passageway 31 into annular recess23 by way of those ports in thes slide valve adjacent the inletpassageway. Guide member 39 prevents the flow of fluid from the recessthrough the remaining ports. Thus, power fluid can flow from the recessonly by passing under one end of the slide valve. This arrangementpermits operation of the slide valve at any radial position of thehammer and valve.

The ports are desirably about midway between the ends of the valvemembers. The width of slide valve guide member 39, i.e., thelongitudinal separation between upper fluid conduit 34 and lower fluidconduit 33, should be slightly greater than the distance spanned byslide valve ports 3% as the valve member moves between its upper andlower positions. This will prevent the flow of power fluid from theannular recess into the upper and lower conduits by way of the ports.The length of the sleeve valve may be approximately equal to the widthof the annular recess in the hammer. This will prevent the simultaneousflow of power fluid to the upper and lower conduits, a condition whichmight cause the percussion motor to stall. The width of the annularrecess is preferably approximately equal to the distance between theupper and lower conduits.

The position of lower guide member 38 can be seen in FIGURE 5. Ribs 47provide support across lower fluid conduit 33 between the guide andhousing 10.

The connection between adapter 16 and anvil 15 has mating splines 17 inthe adapter and anvil to transmit rotary motion from the drill stern andhousing 1.0 to the drill bit. Longitudinal movement produced when thehammer strikes the anvil is permitted by the wide groove 13 which passesover the retainer balls 19. Set screw 20 may be used to close theopening where the balls were inserted.

Various methods may be used in the assembly of this tool. For example,guide members 3'7, 38, 39, 40 and 41, as well as upper head 36, may bestacked on adapter 16 with suitable .spacer elements whereby they willbe held in place by housing 10 when it is connected to the adapter.

From the foreging description of the operation of the tool, it will beunderstood that the hammer moves in response to the inlet pressure ofthe power fluid on one end and the exhaust pressure on the other end.This feature enables the hammer to operate at high velocity deliveringenergy to the bit equal to that obtained with more massive hammers inlower velocity tools.

To obtain the maximum benefit from the slide valve in the power fluidinlet, the valve should operate at a velocity substantially greater thanthat of the hammer. Using the corresponding designations givenpreviously in the relationship for kinetic energy of the hammer and:

V=Velocity g=Acceleration due to gravity When, P, g and S do not vary,it will be seen that:

VOLA/W Thus, the velocity of the slide valve may be increased either byincreasing the net area of the valve member or by decreasing its weight.Our slide valve combines both possibilities. One end of the valve memberis subjected to inlet pressure while the opposite end is exposed toexhaust pressure. The entire cross-sectional area of the member istherefore subjected to the differential pressure. Also, weight of thevalve member is quite small in relation to the weight of the hammer. Thelength'of the slide valve is desirably slightly less than the width ofthe annular recess in the hammer. The width of the rcess may be lessthan twice the length of the hammer stroke. To avoid damage to the tool,the hammer stroke is usually less than one inch. Thus, the ratio A/ Wfor the slide valve may be from 10 to times that of the hammer.Therefore, the slide valve will shift to its alternate position at avelocity from 10 to 100 times that of the hammer, disregarding theeffect of friction. This fast operation will insure the repositioning ofthe valve member in advance of the hammer. Owing to friction effects andfluid leakage between the motor components, it is desirable for theslide valve to have a theoretical velocity at least twice, andpreferably ten times, that of the hammer.

The moving finger valve should extend above the hammer a short distance,preferably about one-quarter to onehalf inch, when flange 26 is at thelower end of cylinder 24. This will stop the exhaust of fluid throughthe finger valve near the end of the hammer upstroke and compress thefluid trapped above the hammer, thereby preventing the hammer fromstriking upper head 36. During the downstroke of the hammer, the fingervalve should be almost flush with the lower face of the hammer. A slightextension, e.g., about one-eighth inch, may be desirable to provide abetter fluid seal between lower fluid conduit 33 and exhaust passageway32 at the start of the upstroke.

This tool may be used with either a liquid or a gaseous power fluid;however, gaseous fluids are preferred. The stresses produced by thesudden closure of the valves are less severe when a compressible fluidis used to drive the tool.

From the above it can be seen that we have provided a percussiondrilling tool wherein the pressure of the power fluid is applied to thehammer throughout substantially the entire stroke. Although thedescription of the apparatus has been limited to our preferredembodiment, it should be understood that other mechanical designs arefunctional equivalents. In some circumstances, it may be desirable touse either the slide valve or the moving finger valve without the other.Either alone will improve the operating efliciency of the equal-areapercussion tool; however, the optimum benefits are obtained when theyare used in combination. Therefore, our invention should be limited onlyby the scope of our claims.

We claim:

1. A percussion drilling tool comprising (1) a hollow cylindricalhousing,

(2) an anvil containing an exhaust passageway, said anvil slidablyconstrained within said housing and so shaped relative thereto thataxial torque may be transmitted therebetween, said anvil protruding fromsaid housing and including coupling means for attaching a drill bit,

(3) a hollow hammer adjacent said anvil, slidably constrained within andclosely fitting said housing, said hammer being shaped to define anannular recess tn the outer surface thereof,

(4) a hollow finger valve slidably disposed in said hammer and longerthan said hammer by approximately the length of stroke of said hammer,the end adjacent said anvil being of shape and alignment to seal saidexhaust passageway,

(5) means within said hammer and responsive to the diflerence inpressure on the ends of said hammer for moving said finger valve in thedirection of the hammer end under greater pressure,

(6) said housing defining a stationary inlet fluid passageway andseparate, stationary upper and lower fluid conduits, the lattercommunicating at all times respectively with the upper and lower ends ofsaid hammer, said upper and lower conduits terminating adjacent saidannular recess and longitudinally separated by a distance approximatelyequal to the width thereof,

(7) an annular slide valve mounted with limited axial movement in saidhousing and about said hammer and closely fitting said housing and saidhammer, said valve being approximately the same width as that of saidannular recess, the upper and lower ends of said slide valve being inconstant fluid communication with said upper and lower fluid conduitsrespectively, said slide valve being interposed between said annularrecess and said upper and lower fluid conduits but so arranged as toadmit fluid continuously from said inlet fluid passageway to saidannular recess, so that differences in fluid pressure between said upperand lower conduits controls the axial displacement of said slide valvein said limited axial movement and thus controls flow of fluid to saidupper and lower fluid conduits, and

(8) a recessed upper head fixed to said housing above said hammer, therecess in said head being shaped and aligned to fit closely the upperend of said finger valve when said hammer is near the top of its stroke.

2. A percussion drilling tool in accordance with claim 1 in which saidfinger valve includes a flange attached thereto and said hammer isshaped to form a cylindrical chamber closely fitting said flange, saidflange and said finger valve forming a piston in said cylindricalchamber, said hammer containing fluid passages connecting respectivelythe top of said hammer with the bottom of said cylindrical chamber andthe bottom of said hammer with the top of said cylindrical chamber.

3. A percussion drilling tool in accordance with claim 1 in which thediameter of said hammer above said annular recess is substantially thesame as the diameter of said hammer below said annular recess.

4. A percussion drilling tool in accordance with claim 1 in which saidslide valve is mounted in a groove in said housing, said groove beingsubstantially centered with respect to the position of said annularrecess in said hammer at the mid-point of its stroke, said inlet fluidpassageway terminating in said groove, said slide valve containingradial ports at least one of which is in constant fluid communicationwith said annular recess and said inlet fluid passageway.

5. A percussion drilling tool in accordance with claim 4 in which theminimum longitudinal separation between said upper and lower fluidconduits is slightly greater than the distance spanned by said radialports in said slide valve as said slide valve moves between its upperand lower positions, the Width of said annular recess is approximatelyequal to said minimum separation between said upper and lower fluidconduits, and the width of said slide valve is slightly less than thewidth of said annular recess in said hammer.

References Cited in the file of this patent UNITED STATES PATENTS1,942,690 Feucht Jan. 9, 1934 2,773,483 Gal et a1 Dec. 11, 19562,800,884 Mori July 30, 1957 2,859,733 Bassinger et a1 Nov. 11, 19582,887,989 Dulaney May 26, 1959 2,947,519 Feucht Aug. 2, 1960 2,979,033Bassinger Apr. 11, 1961 3,101,796 Stall et a1. Aug. 27, 1963

1. A PERCUSSION DRILLING TOOL COMPRISING (1) A HOLLOW CYLINDRICALHOUSING, (2) AN ANVIL CONTAINING AN EXHAUST PASSAGEWAY, SAID ANVILSLIDABLY CONSTRAINED WITHIN SAID HOUSING AND SO SHAPED RELATIVE THERETOTHAT AXIAL TORQUE MAY BE TRANSMITTED THEREBETWEEN, SAID ANVIL PROTRUDINGFROM SAID HOUSING AND INCLUDING COUPLING MEANS FOR ATTACHING A DRILLBIT, (3) A HOLLOW HAMMER ADJACENT SAID ANVIL, SLIDABLY CONSTRAINEDWITHIN AND CLOSELY FITTING SAID HOUSING, SAID HAMMER BEING SHAPED TODEFINE AN ANNULAR RECESS TN THE OUTER SURFACE THEREOF, (4) A HOLLOWFINGER VALVE SLIDABLY DISPOSED IN SAID HAMMER AND LONGER THAN SAIDHAMMER BY APPROXIMATELY THE LENGTH OF STROKE OF SAID HAMMER, THE ENDADJACENT SAID ANVIL BEING OF SHAPE AND ALIGNMENT TO SEAL SAID EXHAUSTPASSAGEWAY, (5) MEANS WITHIN SAID HAMMER AND RESPONSIVE TO THEDIFFERENCE IN PRESSURE ON THE ENDS OF SAID HAMMER FOR MOVING SAID FINGERVALVE IN THE DIRECTION OF THE HAMMER END UNDER GREATER PRESSURE, (6)SAID HOUSING DEFINING A STATIONARY INLET FLUID PASSAGEWAY AND SEPARATE,STATIONARY UPPER AND LOWER FLUID CONDUITS, THE LATTER COMMUNICATING ATALL TIMES RESPECTIVELY WITH THE UPPER AND LOWER ENDS OF SAID HAMMER,SAID UPPER AND LOWER CONDUITS TERMINATING ADJACENT SAID ANNULAR RECESSAND LONGITUDINALLY SEPARATED BY A DISTANCE APPROXIMATELY EQUAL TO THEWIDTH THEREOF, (7) AN ANNULAR SLIDE VALVE MOUNTED WITH LIMITED AXIALMOVEMENT IN SAID HOUSING AND ABOUT SAID HAMMER AND CLOSELY FITTING SAIDHOUSING AND SAID HAMMER, SAID VALVE BEING APPROXIMATELY THE SAME WIDTHAS THAT OF SAID ANNULAR RECESS, THE UPPER AND LOWER ENDS OF SAID SLIDEVALVE BEING IN CONSTANT FLUID COMMUNICATION WITH SAID UPPER AND LOWERFLUID CONDUITS RESPECTIVELY, SAID SLIDE VALVE BEING INTERPOSED BETWEENSAID ANNULAR RECESS AND SAID UPPER AND LOWER FLUID CONDUITS BUT SOARRANGED AS TO ADMIT FLUID CONTINUOUSLY FROM SAID INLET FLUID PASSAGEWAYTO SAID ANNULAR RECESS, SO THAT DIFFERENCES IN FLUID PRESSURE BETWEENSAID UPPER AND LOWER CONDUITS CONTROLS THE AXIAL DISPLACEMENT OF SAIDSLIDE VALVE IN SAID LIMITED AXIAL MOVEMENT AND THUS CONTROLS FLOW OFFLUID TO SAID UPPER AND LOWER FLUID CONDUITS, AND (8) A RECESSED UPPERHEAD FIXED TO SAID HOUSING ABOVE SAID HAMMER, THE RECESS IN SAID HEADBEING SHAPED AND ALIGNED TO FIT CLOSELY THE UPPER END OF SAID FINGERVALVE WHEN SAID HAMMER IS NEAR THE TOP OF ITS STROKE.